<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
<script>
//function (){
	
//}
window.onload=function(){
	var oUl=document.getElementById('ul1');
	var cBox=oUl.getElementsByClassName('box');
	
	alert(cBox.length);
		
};
</script>
</head>

<body>
<ul id="ul1">
	<li class="box"></li>
    <li></li>
    <li class="box"></li>
    <li></li>
</ul>
</body>
</html>
